The terms “audio” and “audio signal” are used herein to refer to any of a wide variety of audio signals or sources such as music, speech, tones, alerts, and the like. Audio signals refer to analog or digital signals. For digital audio, data compression may be used via audio coding. There are many audio coding standards that facilitate the coding of digital audio. Examples include standards defined by the motion pictures expert group (MPEG), windows media audio (WMA) standards, and standards by Dolby Laboratories, Inc. Moreover, many audio coding standards continue to emerge, including the digital MP3 standard and successors to the MP3 standard, such as the advanced audio coding (AAC) standard used in “iPod” devices sold by Apple Computer, Inc.
Many different types of devices can deliver audio to users. Examples of such audio devices include music players, wireless mobile devices, wireless communication devices, such as radio telephones, direct two-way communication devices (sometimes called walkie-talkies), desktop and laptop computers, workstations, satellite radio devices, intercom devices, radio broadcasting devices, on-board computers used in automobiles, watercraft and aircraft, and a wide variety of other devices.
In many situations, two or more audio signals (which may be analog or digital signals) are processed simultaneously by a given audio device. In the case of radio telephones that also provide digital music capabilities, for example, the music output may conflict with the audio associated with an incoming telephone call. To address this conflict, conventionally, an incoming telephone call preempts any music output. In this case, the music may be muted when an incoming telephone call is received.